The present invention generally relates to fluid dispensers, and more specifically, the present invention relates to fluid dispensers which accurately control the amount of fluid dispensed. The present invention also relates to methods of dispensing fluid in a controlled manner. One specific example of a fluid dispenser according to the present invention is a paint colorant dispenser.
Paints are made in a vast number of different colors and shades of colors. Each specific paint color has a specific formula of components to provide the desired color. A paint formula generally includes a relatively large amount of a base and smaller amounts of one or more colorant colors. Each colorant color is measured according to the formula and dispensed from a bulk colorant supply, added to the base, and then mixed to produce the desired paint color.
Existing colorant dispensers have been used in retail paint supply stores and hardware stores, for example. Existing colorant dispensing equipment has included manual and automated machines. Automated colorant dispensing equipment can include several bulk colorant containers, in which each colorant container is connected to an inlet of a fluid pump. The outlet of the fluid pump is connected to a 3-way valve which has a dispense outlet connected to a dispense nozzle and a by-pass outlet connected to a recirculation fluid line. Either one motor may drive all pumps or several pumps may be driven by a single motor through a common drive mechanism or each pump may be driven by an individual motor. When an amount of colorant is dispensed, the motor drives the pumps and the 3-way valve for the particular colorant is opened to allow the colorant to be dispensed through the nozzle. The time period that the valve remains open determines the amount of colorant dispensed. The other 3-way valves, which are all being simultaneously driven by the motor, are in a by-pass mode so that the colorant recirculates back into its container rather than being undesirably dispensed.
However, existing colorant dispensing equipment can be improved. The colorant dispensing equipment utilizes a 3-way valve for each colorant container, which increases the equipment costs and manufacturing costs. Also, the plurality of 3-way valves tend to be a significant source of maintenance and service problems. Furthermore, the accuracy of the amount of colorant dispensed using the pump and valve arrangement can be improved. Also, a by-pass colorant flow path is needed because the single motor simultaneously operates all of the pumps. It is desired to more accurately control the amount of colorant dispensed so that the resulting paint color for any particular formula is consistent. Greater accuracy and control over the colorant dispensing process provides greater consistency in paint color for any given formula.
One paint colorant dispenser according to the present invention utilizes a nutating pump and a computer control system to control the pump. Nutating pumps have a piston which is positioned inside of a housing having a fluid inlet and a fluid outlet. The piston simultaneously slides axially and rotates inside of the housing. Existing nutating pumps have been operated by rotating the piston through a full 360xc2x0 rotation and corresponding linear travel of the piston. Such piston operation results in a specific amount of fluid pumped by the nutating pump with each revolution. Accordingly, the amount of fluid pumped for any given nutating pump is limited to multiples of the specific volume. If a smaller volume of fluid is desired, then a smaller sized nutating pump is used or manual calibration adjustments are made to the pump. For example, in paint coloranting a minimum dispense can be about {fraction (1/256)}th of a fluid ounce. At such a small dispense, the motor would have had to run at excessive speeds to dispense larger volumes of colorant (multiple full revolutions) in an appropriate time period. In order to minimize the dispense motor speed, a partial-revolution dispense for a larger capacity nutating pump would be advantageous. However, using a partial revolution to accurately dispense fluid is difficult due to the non-linear output of the nutating pump dispense profile vs. angle of rotation. Accordingly, needs exist to automatically control and vary the volume amount of fluid pumped by nutating pumps.
The present invention provides new colorant dispensers which accurately, consistently, and effectively dispense fluid. The invention is described as embodied in a paint colorant dispenser; however, the invention can be utilized to dispense any desired fluid. For example, the fluid dispensers can be used to dispense pharmaceuticals, cosmetics, inks, and other fluids at controlled volumes.
The paint colorant dispenser has a computer control system which operates a stepper motor or other incrementally controlled drive that drives a valveless pump, such as a nutating pump. Paint color formulas are stored in the computer control system and selected by an operator to mix a desired color of paint. The nutating pump pumps colorant from a bulk container to a dispense nozzle based on signals sent by the computer control system according to the paint color formula. The computer control system operates the stepper motor and the nutating pump such that the pump piston rotates less than a full 360xc2x0 revolution for each step of the stepper motor. For example, 400 steps may be required for one full 360xc2x0 revolution. The stepper motor and the nutating pump are rotated through a desired number of steps to dispense a desired amount of fluid.
The fluid dispense system having the nutating pump and computer control system accurately dispenses both large and small quantities of fluid. The computer control system controls the stepper motor and nutating pump to dispense a predetermined amount of fluid by dividing one full 360xc2x0 pump piston revolution into several partial dispenses or segments.
The nutating pump of the present invention can be adjustable. For example, the angle between the axis of the nutating pump piston and the axis of the stepper motor shaft can be adjusted by an actuator. The computer control system sends signals to the actuator to operate the actuator which positions the nutating pump piston at a desired angle. The automated nutating pump angle adjustment effectively adjusts the pump fluid output through computer control.
Another nutating pump adjustment also provides for changing the pump fluid output. In this adjustment, the distance that a spherical bearing is off-set from the stepper motor shaft can be varied. The bearing off-set adjustment alters the fluid output of the nutating pump, and can be used to calibrate the pump, for example.
Various advantages of the present invention can become apparent upon reading this disclosure including the appended claims with reference to the accompanying drawings. The advantages may be desired, but not necessarily required to practice the present invention.